This invention is process for preparing light sensitive aryl-diazide-sulfonic acids. These compounds are useful as chemical intermediates in the preparation of photoresist compositions; see, for example: Light Sensitive Systems; Kosar, Jr.; Chapter 7.4, John Wiley & Sons, NY, NY 1965, which is incorporate herein by reference.
Typically, in the prior art, light sensitive aryl-diazide-sulfonic acids are prepared by first nitrosating a hydroxy-substituted benzene or naphthalene sulfonic acid in dilute aqueous acid solution by the addition of sodium nitrite. The nitroso compound is then isolated as a precipitate and washed to remove unreacted starting materials and impurities. The nitroso intermediate is then reduced to an amine intermediate using sodium borohydride or sodium dithionite. The amine intermediate is recovered as a precipitate and washed to remove unreacted starting materials and impurities. The amine is then reslurried in water and contacted with sodium nitrite at low pH to form the diazide compound.
In contrast to above multistep, multi-reactor process of the prior art, the process of this invention eliminates the need to isolate and purify the intermediates which are maintained in aqueous solution. Impurities, unreacted starting materials etc. are removed by filtration of reaction medium. In this manner, high productivity, high yield and reduced costs are achieved by removing the impurities which are present in small quantities as precipitates--not as was done in the prior art, isolating and purifying the intermediate reaction products. Additional advantages include increased yield, high product purity, high reactor utilization and reduced waste discharge streams.